1. Field of the Invention
The present invention relates to a projector, particularly to a projector having a simple structure, to prevent a phase shift caused by a temperature difference between a plurality of light sources and to easily control temperatures of the light sources.
2. Description of the Related Art
A projector generally displays a desired picture by projecting image beams onto a screen, and is applied in a projection television having a similar projecting apparatus to form a picture.
The projector may be either a transparent-type projector to form a picture with light passing through a display device, or a reflection-type projector to form a picture onto a screen with light reflected by the display device.
A liquid crystal projector using an LCD panel as the display device of the projector has been developed. As various technologies are developed for an optical lamp device affecting color and resolution of a displayed picture, the liquid crystal projector generally may be either an SLPS (single LCD panel system) using one LCD panel, or a TLPS (triple LCD panel system) to split light from the optical lamp device into three primary colors and project the light using the LCD panels corresponding to the three primary colors.
FIG. 1 is a schematic view of a projector according to a conventional TLPS method. As illustrated, the projector using three LCD panels includes a light source 100 to emit light, two fly-eye lenses 200 to synthesize and split the light emitted from the light source 100, and a PBS array 300. The projector further includes two primary light collection lenses 400, four total reflection mirrors 500, two dichroic mirrors 510, a magnifying lens 520, and secondary light collection lenses 600a, 600b, and 600c to improve the straightness of the light reflected by the mirrors. The projector further includes three LCD panels 610a, 610b, and 610c to transform the light having the straightness improved by the secondary light collection lenses 600a, 600b, and 600c into respective colored lights having color signals R, G, and B, an optical synthesizer 700 to synthesize the colored lights having color signals R, G, and B from the LCDs 610a, 610b, and 610c, and a projection lens 800 to magnify and project the light synthesized by the optical synthesizer 700.
An operation of the projector having the above configuration will be described hereinbelow. The light emitted from the light source 100 is synthesized and split through the fly-eye lenses 200, the PBS array 300, the primary light collection lenses 400, the total reflection mirror 500, the dichroic mirrors 510, and the magnifying lens 520. Also, the light split by the dichroic mirrors 510 goes through a light modulation process by the LCD panels 610a, 610b, and 610c representing the color signals R, G, and B, respectively.
The respective colored lights representing the color signals R, G, and B by the LCD panels 610a, 610b, and 610c are synthesized by the optical synthesizer 700. The light synthesized by the optical synthesizer 700 is magnified and projected through the projection lens 800.
However, the projector having the above configuration has a disadvantage because a structure thereof becomes complicated and the brightness decreases due to decrease in a transmission rate of the light.
To solve this problem, Korean Patent First Publication No. 2003-57751 illustrates a projection display apparatus using an LED as a light source and providing individual lights to respective LCD panels. However, since such configuration also requires a plurality of LEDs (light emitting diodes) as the light source, a temperature difference among the plurality of LEDs causes a problem such as a phase shift which shifts the image.